1. Field of the Invention
This invention is in the field of liquid compositions containing high concentrations of active ingredients which are useful in the preparation of surface coatings. More particularly this invention relates to compositions containing bis-(alkoxymethyl)urons and reactive polymers containing hydroxyl or carboxyl groups.
2. Description of the Prior Art
Surface coating compositions containing polyfunctional resins and aminoplast crosslinking agents are well known in the art. In general the polyfunctional resin is of high molecular weight and is compounded with the aminoplast in solution in an organic solvent to provide a solution containing between 10 and 50 weight percent of active ingredients, i.e., the ingredients which interact to provide high molecular weight crosslinked resins when the solvent is driven off and the residue is baked. Alternatively the polyfunctional resin may be prepared as an aqueous dispersion in water or a "non-aqueous" dispersion in an organic liquid which is a non-solvent for the resin and the dispersion is compounded with the aminoplast crosslinking agent. Like the coating solutions, non-aqueous dispersions yield large quantities of organic vapors when they are dried and present an air pollution problem. Moreover aqueous and non-aqueous dispersions may not flow adequately at the baking step so that the surface coatings lack gloss and coherence and do not provide adequate corrosion protection. Also aqueous systems tend to blister at the drying step.
Dry powder compositions containing low molecular weight polyfunctional resins and aminoplasts have been developed in recent times to eliminate the organic liquid from coating compositions. Such powders are applied by electrostatic or fluidized bed processes. However, the powders tend to flow and clump in storage and become difficult to apply uniformly and evenly or they lack adequate flow at the baking temperature so that they also provide coatings which lack gloss and coherence.
A need therefore exists for surface coating compositions which comprise polyfunctional resins and aminoplast crosslinking agents as the active ingredients, in which the organic moiety is comprised of at least 80 volume percent of these active ingredients and which is liquid at room temperature. A further need exists for such liquid compositions which can be applied by disc or bell spray, by knife or roll coat or by air spray.